Add Deferred state to Collaborator review workflow?

We have several projects where funding is volatile, and work efforts get shut off/turned on with very little notice.

Collaborator reviews stay open indefinitely, which is not ideal. Users also don't like pages of stagnant reviews on their dashboards.  We would like to move these reviews to a deferred state, rather than have to cancel them, since they may resume again in the future.  It makes sense, and would be a useful feature.